Sciencemadness Discussion Board - PETN recrystallisation procedure for LOW density

PETN recrystallisation procedure for LOW density

Gargamel - 5-8-2015 at 07:06

Hi guys,

in most professional recrystallisation procedures people want to grow high density stuff.

In this case I want something as DDT friendly as possible. To my knowledge this means a very small crystal size.

My strategy is to create a warm Acetone solution and let it drip into ice water to give the crystals the shortest possible time to form.

How would you grow your crystals in this case? Are there any other tricks?

I've read about ball milling, but I'd rather feel uncomfortable about that

greenlight - 5-8-2015 at 07:24

I have been mucking around with recrystallizing PETN for a couple of months now for making plastic explosive after getting some advice from others on the forum.

The method I have stuck to using is dissolving the PETN in minimal near boiling acetone and letting it cool to about room temperature before pouring very slowly (you could try dripping) into about the same volume of ice cold water.
This gives a large amount of small crystals and some powder which I think works well to fill in the gaps.
The last batch I added 5 grams of RDX to the 75 grams PETN as well during the recrystallization.
I have some decent plastic explosive I just made using this technique with 15% Polybutene and 1% motor oil @ about 1.43 density.
10 grams easily punches a clean hole through a steel plate just over 3 mm thick which isn't really a tough target but the size of the lump of plastic look very small due to the density.

VladimirLem - 5-8-2015 at 11:47

Quote: Originally posted by Gargamel

Hi guys,

in most professional recrystallisation procedures people want to grow high density stuff.

In this case I want something as DDT friendly as possible. To my knowledge this means a very small crystal size.

sounds like your real problem is the detonator cap, not the high explosive itself...PETN normaly is pretty easy to ignite...

and i would try big crsytals instead of fine powdered material...just crash the whole solution into water, without any delay...this will make a "powder" like dry sand at a beach, with a low density, when not compressing (0.8-1.0g/cm3)
With fine material, you will fill the gaps between the crystals (even when not compressing) and making is a bit more "difficult"

to ignite, i guess...

NeonPulse - 5-8-2015 at 15:35

Just crash the acetone solution into iced water with heavy agitation or mechanical stirring and that should do it for you

nux vomica - 5-8-2015 at 19:42

Quote: Originally posted by NeonPulse

Just crash the acetone solution into iced water with heavy agitation or mechanical stirring and that should do it for you

I agree with Neon I use petn made this way in my ebw dets and it is fine enough to detonate every time .
Nuxy.

greenlight - 5-8-2015 at 20:11

Does fast addition of the PETN/acetone solution to the ice water with rapid stirring give crystals that would still be good to plasticize?

[Edited on 6-8-2015 by greenlight]

nux vomica - 5-8-2015 at 22:39

Quote: Originally posted by greenlight

Does fast addition of the PETN/acetone solution to the ice water with rapid stirring give crystals that would still be good to plasticize?

[Edited on 6-8-2015 by greenlight]

Sorry Greenlite I cant help you there someone should have a answer, ive only just found some PB to make some plastic up I have always used it straight nuxy

[Edited on 6-8-2015 by nux vomica]

greenlight - 6-8-2015 at 02:38

What are you using for the PB?
Is it bird repellant?
Are you plasticizing PETN or ETN?

nux vomica - 6-8-2015 at 02:57

Quote: Originally posted by greenlight

What are you using for the PB?
Is it bird repellant?
Are you plasticizing PETN or ETN?

Cant get bird repellant or rat boards , animal lovers have pushed government to ban it ,I am hopeing a sticky bug trap from major hardware chain here is pb
I am going to plasticize etn as I have 500grms of sweetener and only 50 grms of penta. Cheers Nuxy.

[Edited on 6-8-2015 by nux vomica]

greenlight - 6-8-2015 at 03:39

I can't get the bird repellent here either i searched many hardware and garden stores after Neonpulse told me to use it.
Its easy to ontain on ebay which was my source.

Heres one: http://m.ebay.com.au/itm/Bird-Proof-gel-apply-to-roosting-ne...

[Edited on 6-8-2015 by greenlight]

nux vomica - 6-8-2015 at 04:15

I actually need to put some spikes on my pergola to keep the birds out might try and sneak a tube in the order ,I will tell the wife its to keep the birds away luv.

I assume it is the same consistency as clear silicon. ?
The boards I have I am sure are pb but its quite thick and not like silicon at all so I was going to use more oil to soften it up when I use it nuxy.

greenlight - 6-8-2015 at 05:51

Yeah it is about the same consistency as clear silicon and very sticky and tacky and never dries.
Your boards may have something else added into them as well

Hennig Brand - 6-8-2015 at 08:56

Quote: Originally posted by nux vomica

Quote: Originally posted by NeonPulse

Just crash the acetone solution into iced water with heavy agitation or mechanical stirring and that should do it for you

I agree with Neon I use petn made this way in my ebw dets and it is fine enough to detonate every time .
Nuxy.

Yeah, same simple method I use with decent results.

Regarding PB repellents, I have found the bird repellant PB formulations works best without added oil or at least very, very, little. The resultant putty explosive gets very soft, oily and sticky when much oil is added and it also doesn't hold together nearly as well as when the repellant is used straight or with minimal oil/softener.

VladimirLem - 6-8-2015 at 09:53

Quote: Originally posted by greenlight

Does fast addition of the PETN/acetone solution to the ice water with rapid stirring give crystals that would still be good to plasticize?

[Edited on 6-8-2015 by greenlight]

from my experience definitivly not when using high concentrated HNO3

I read about a method, placing the hot aceton/petn solution in a polysterol container and then putting it into a freezer for 10+h, so the petn crystalizes extremely slow and you will get extremely fine crystals...

When making PETN from 65-70% HNO3 (+H2SO4 of course), i had with this method very fine powdered PETN (still not sure if Tri or Tetra nitrate) - like tiny needles, perfect to compress...should be pretty good for chewing gum

i really wonder how the acid concentration has such an influence to the crystal shape...the material was the same quality/batch

nux vomica - 6-8-2015 at 17:04

I had better get some etn plastic made soon to test the 60 degree copper cones I have been working on at the moment.
Nuxy .

[Edited on 7-8-2015 by nux vomica]

greenlight - 7-8-2015 at 02:29

That tooling looks awesome Nux, I have been looking for a former like that for conical shaped charge liners for a long time.
Where did you buy them, or did you make them yourself?

nux vomica - 7-8-2015 at 03:06

Quote: Originally posted by greenlight

That tooling looks awesome Nux, I have been looking for a former like that for conical shaped charge liners for a long time.
Where did you buy them, or did you make them yourself?

Homemade, I am lucky and have a lathe at home and I do all of the more simple turning and milling at work, so I can slip my home jobs in between work ones.
The first two cones are annealed between getting formed into a polyurethane rubber pad in the tube to the right then I anneal then press into the 60 degree plastic former, it is quiet a simple process when you have worked out the bugs nuxy.

[Edited on 7-8-2015 by nux vomica]

Gargamel - 7-8-2015 at 13:53

Thank you for your answers.

Somehow I messed this up, using the least possible amount of acetone at ~55°C (started to boil) and crashing it into ~8°C Water somehow produced a lot of larger crystals. I was stirring like crazy and poured very slowly.

The density is now much greater than the unrecrystalised stuff.
Not good for DTT, rather for most other applications.

I made PETN some time before, but I did not take detailed notes back then. That stuff was much more fluffy. More Acetone would be my guess.

So the perfect DDT PETN "recipe" is still to be developed...

Nux, I envy your equipment. Cool stuff.

greenlight - 8-8-2015 at 09:16

I always use that procedure and get a nice mix of fluffy powder/granules. Good to plasticize.
Maybe you could try dumping it in fast like others outlined above otherwise just keep trying by recrustallizing the same stuff until you get a desired result. I just re-read your post and realized that you are looking for PETN to attain deflag-det transition with only and not plasticization.
Are you trying to build explosive bridgewire detonators?
If so I may be wrong as I haven't attempted to make one but wouldn't ETN be easier to acheive DDT with than PETN due to it being more heat sensitive?

[Edited on 8-8-2015 by greenlight]

Gargamel - 10-8-2015 at 01:32

Quote:

Are you trying to build explosive bridgewire detonators? If so I may be wrong as I haven't attempted to make one but wouldn't ETN be easier to acheive DDT with than PETN due to it being more heat sensitive?

Yes and yes. But I have personal reasons to prefer PETN.

Strictly speaking it's not about DDT but shock sensitiveness.
ETN would be slightly superiour, no doubt.

nux vomica - 10-8-2015 at 02:51

Quote: Originally posted by Gargamel

Quote:

Yes and yes. But I have personal reasons to prefer PETN.

Strictly speaking it's not about DDT but shock sensitiveness.
ETN would be slightly superiour, no doubt.

Your petn will be fine just go for it my petn is not to the recomended standards I am sure, but I still can set it off just as easy as etn with my ebw setup.

I would be more worried about my fireing set eg capacitors ,spark switch ebw head, fireing voltage, get those right and the petn shouldn't be a issue nuxy.